This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Project 1: Oxidoreductase: Aldose reductase (AR) is an NADPH dependent oxidoreductase that catalyzes the reduction of a wide variety of aldehydes including glucose. It has been shown that increased flux of hexoses via the AR catalyzed pathway is one of the underlying causes of tissue injury and dysfunction associated with hyperglycemic states such as diabetes mellitus. Clinical trials with AR inhibitors have yielded uncertain results and the long-term efficacy of these drugs in treating diabetic complications remains to be demonstrated. AR has been crystallized with several compounds sorbitol, fidarestat, zopolrestat, tolrestat, sorbinil, citrate, cacodylate, glucose 6-phosphate, oxazolecarbamate, WF-3681 and IDD384 in more than one crystal form. Employing structure-based inhibitor design approach we have demonstrated a novel class of compounds as AR inhibitors. Our current aim is to collect x-ray diffraction data at SSRL to determine the complex structures of these lipid based compounds with wild-type and mutant forms of AR. Crystal structures of AR with the lipid based compounds will provide the specific interactions between the amino acid residues of AR and these compounds. The knowledge of the interactions will help to us distinguish the unique contacts responsible for varied inhibition properties in combination with biological and clinical data. Project 2: Nucleic acid binding protein: Protection from DNA invasion is afforded by restriction-modification systems in many bacteria. The efficiency of protection depends crucially on the relative expression levels of restriction versus methytransferase genes. This regulation is provided by a controller protein, named C protein. Studies of the BclI system in E. coli suggests that C.Bcll functions as a negative regulator for M.BclI expression, implying a role in defense of foreign DNA during virus infection.